Heater including a plurality of heat generation members, fixing apparatus, and image forming apparatus

Abstract

The heater including a substrate, a first heat generation member, a second heat generation member having a length substantially a same in a longitudinal direction as a length of the first heat generation member, a third heat generation member having a length shorter than lengths of the first heat generation member and the second heat generation member in the longitudinal direction, and a fourth heat generation member having a length shorter than length of the third heat generation member in the longitudinal direction, wherein the first heat generation member, the second heat generation member, the third heat generation member and the fourth heat generation member are arranged on the substrate.

What is claimed is: 
     
       1. A heater comprising:
 a substrate; 
 a first heat generation member; 
 a second heat generation member having a length substantially equal in a longitudinal direction to a length of the first heat generation member; 
 a third heat generation member having a length shorter than the lengths of the first heat generation member and the second heat generation member in the longitudinal direction; 
 a fourth heat generation member having a length shorter than the length of the third heat generation member in the longitudinal direction; and 
 a fifth heat generation member having a length shorter than the length of the fourth heat generation member in the longitudinal direction, 
 wherein the first heat generation member, the second heat generation member, the third heat generation member, the fourth heat generation member, and the fifth heat generation member are arranged on the substrate, 
 the first heat generation member is arranged at one end of the substrate in a width direction, 
 the second heat generation member is arranged at another end of the substrate in the width direction, to be symmetrical with the first heat generation member, and 
 the third heat generation member, the fourth heat generation member, and the fifth heat generation member are arranged between the first heat generation member and the second heat generation member in the width direction of the substrate; and 
 a first contact to which one end of each of the first heat generation member and the second heat generation member is electrically connected; 
 a second contact to which another end of each of the first heat generation member and the second heat generation member and one end of the third heat generation member are electrically connected; 
 a third contact to which another end of the third heat generation member and one end of the fourth heat generation member are electrically connected; 
 a fourth contact to which another end of the fourth heat generation member and one end of the fifth heat generation member are electrically connected; and 
 a fifth contact to which another end of the fifth heat generation member is electrically connected. 
 
     
     
       2. A heater according to  claim 1 , wherein the first heat generation member, the third heat generation member, the fifth heat generation member, the fourth heat generation member, and the second heat generation member are arranged in that order in the width direction of the substrate. 
     
     
       3. A heater according to  claim 1 , wherein the third heat generation member and the fourth heat generation member are arranged to be symmetrical in the width direction of the substrate. 
     
     
       4. A heater according to  claim 1 , wherein a value of a combined resistance of the first heat generation member and the second heat generation member is smaller than a value of a resistance of the fifth heat generation member. 
     
     
       5. A heater according to  claim 1 , wherein a value of a combined resistance of the first heat generation member and the second heat generation member is smaller than a value of a resistance of the third heat generation member and smaller than a value of a resistance of the fourth heat generation member. 
     
     
       6. A heater according to  claim 1 ,
 wherein a relationship of R 1 ×L 1 >R 2 ×L 2  is satisfied, 
 where L 1  is defined as a length of the third heat generation member in the longitudinal direction, R 1  is defined as a value of a resistance of the third heat generation member, L 2  is defined as a length of the fourth heat generation member in the longitudinal direction, and R 2  is defined as a value of a resistance of the fourth heat generation member. 
 
     
     
       7. A fixing apparatus for fixing an unfixed toner image borne by a recording material, the fixing apparatus comprising:
 a heater according to  claim 1 ; 
 a first rotary member heated by the heater; and 
 a second rotary member forming a nip portion with the first rotary member film. 
 
     
     
       8. A fixing apparatus according to  claim 7 , wherein the first rotary member is a film. 
     
     
       9. A fixing apparatus according to  claim 8 ,
 wherein the heater is provided in an inner space of the film, and 
 wherein the nip portion is formed by the heater and the second rotary member via the film. 
 
     
     
       10. A fixing apparatus according to  claim 7 , wherein at a predetermined position in the longitudinal direction, a distance from a position of a center of rotation of the second rotary member to a heat generation member having a shortest length in the longitudinal direction among other heat generation members except for the first heat generation member and the second heat generation member is shorter than a distance from the position of the center of rotation of the second rotary member to a heat generation member except for the heat generation member having the shortest length among the other heat generation members. 
     
     
       11. An image forming apparatus comprising:
 an image forming unit configured to form an unfixed toner image on a recording material; and 
 a fixing apparatus according to  claim 7 , 
 wherein the fixing apparatus is configured to fix the unfixed toner image on the recording material.